Walking dead keep telling Coming soon on iphone?

So I tried to download the walking dead on my iphone 5, and i can only play first episode, game keep telling me on other episodes "coming soon" how can i buy them? There's no option to get them all i can see is "coming soon", i've re installed game, turned off and on my iphone! Still there's no option to get all episodes, please help if you can i really want to play whole game! Thanks!

Added (1). There's no buy button, it says coming soon!

There should be a buy button that would send you this